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Guest FRI737

737NG Approach Speeds

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Guest FRI737

Hi all,question for 737NG experts and real life pilots:I

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Guest Zapper

Hi StefanWell you have asked quite a few Q's there :)Whilst not having done an actual comparison to real world my feel of the PMDG product is such that it is quite accurate in its FM.The normal 737NG landing flap is 30 or 40 depending on runway length, weight, wind etc. Most -800 operators tend to use Flap40 to save on brake and tyre wear but it is a little harder to land smoothly. That said, any real world pilot doesn'tgive a tinkers cuss about 'greasers'. The whole aim is to land bang in the middle of the TDZ and right on Vref. This is all that counts IRL ... as long as you don't turn the aft fusleage into a banana :DComparing to the relatively nose-low attitude of a straight wing type on approach the deck angle in a jet seems quite high because of given the problems of low speed and swept wings. In fact you rarely have the deck angle much more than 2degrees below the horizon.Another example is on takeoff.. deck angles of up to 20 degrees are quite common whereas a straight wing aircraft would be about 10 degrees max.Approaches are normally flown at the Bug Speed indicated on the speed tape and FMS INIT/REF Page for the current flap setting.Jets are not really meant to be flown level with gear and flap out for a few reasons: Lots of un-neighbourly noise, high fuel flow etc.In the interests of operating the aircraft as economically as possible the aim of the game is to close the thrust levers at top of descent and they stay against the idle stops until about 500' AGL on approach. Now if you want to do this IRL then it means flying into the 3 degree GS for an ILS from above. VNAV does an excellent job of this in the real aeroplane although some of my colleagues disagree as it can test your nerve a bit :)The reason we train ppl to fly level and intercept the GS from below is that in the early parts of you jet time it is very easy to get high and fast and is quite difficult to correct if you do. Old saying: "You can be fast or high, but not both"The DES and APP is the hardest thing about flying a jet and it is in this area that most people fail a line check. However, once you have really got your head wrapped around the DES profile and hands on the aeroplane though it is no problem to fly flight idle approaches to say 1200' AGL. We do this because in this enlightened age we all want to have the aircraft stabilised in the landing configuration, speed within 10kts of target, engines spooled up, checklist complete etc by 1000' and most companies REQUIRE a mandatory GoAround if these conditions are not met by 500'VRef is 1.3*Vs in the particular landing configuation so if we select Flap 30 on the INIT/REF page then the Vref bug will be set at Vref+5 by the FMS and this is where the Autothrottle is aiming to keep the speed. It is set as Vref+5 by default and this 'additive' may be increased to as much as Vref+20 if wind/gust etc is involved. Usually the additive is half the headwind component plus all of the gust factor but never more than 20kts in total. It is this figure that you select in LS 5R when setting up the FMS for APP.Personally I fly the -800 at flap 5 and flight-idle (in nil wind) down the GS and call for 'Gear Down, Flap15' at about 1300', call for "Landing Checklist down to Flaps' and then have Flaps 30 or 40 set by 1100' AGL to meet the company criteria for a stabilised approach.This enough info?Brad Marsh

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Guest FRI737

Brad,thanks for your detailed answer.Of course a CDA is always the best way to bring your 737 down but unfortunately a level-off during approach can

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Guest tmetzinger

>VRef is 1.3*Vs in the particular landing configuation so if we>select Flap 30 on the INIT/REF page then the Vref bug will be>set at Vref+5 by the FMS and this is where the Autothrottle is>aiming to keep the speed. .This may be a cause of the confusion - I believe that the PMDG FMS sets the bug to Vref, not VRef+5. I'll confirm today.I also like that you hold the gear and flaps until 1300 or so, instead of dropping them at the FAF - I'll try that today and see if I have any problems slowing to Vref+5 by 1000 AGL, without violating any flaps limitations.

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Guest FRI737

Good point, never paid attention to that. If you

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Guest tmetzinger

>This may be a cause of the confusion - I believe that the PMDG>FMS sets the bug to Vref, not VRef+5. I'll confirm today.>I confirmed this - the FMS sets the "ref" bug to Vref, and ignores the +5 set on the approach ref page. However, according to Bulfer, this behavior is correct. If you remain in VNAV for the approach (not applicable to ILS), the FMC speed set for landing flaps WILL include the wind correction.So if you are flying a non-precision approach in LNAV/VNAV, your speed will reflect the Vref + the wind correction set on the APPROACH REF page, once you set the appropriate flaps. i.e. flaps 30 Vref is 130, wind correction +7, when you set flaps 30, VNAV will command a speed of 137.On an ILS, when you intercept the glideslope, VNAV drops out and you're in LOC for roll, GS for Pitch, and SPD for speed. You have to manually set the reference speed, and you should set the speed ABOVE the ref bug by whatever factor you like.

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Guest HepburnUGA

Just so that I fully understand.The Vref values displayed by the FMC do NOT have the wind correction. However, if you leave the plane in VNAV, the wind correction will be automatically added to Vref(flap selection).If you are flying using the APPR mode, then the wind correction factor needs to be applied to displayed Vref via SPD?Thanks!Jeff

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Guest boxjockey99

Just to put my two peneth worth in and hopefully un tangle the complex jargon that is happening here (not that that is a bad thing) but here is what we fly on the 300 series and what we set in the MCP:Initial approach 210 (220 above 53,000kg) min cleanAt 210 take flap 1 set MCP speed 190at 200 take flap 5 set MCP speed 180keep the flap 5 config all the way till you see the G/S start to move down from the top.As G/S moves down select GEAR DOWN, FLAP 15, set MCP speed 150As G/S moves to 1 dot above take flap 25 set MCP speed 140 (or Vref+5 if greater)Just before G/S intercept take flap 30 or 40 set MCP speed Vref+5I have no real world experience on the NG but on our 300's we use the APR mode and set MCP speed manually which sets the orange bug on the ASI. VNAV is not used once on the ILS. We can use Vnav to fly the initial approach and it will limit its speeds with the selected flap etc but once onto the LOC we would hit APR mode and then set all the speeds in the speed window.Hope that is of some use to youKris

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Guest HepburnUGA

Hey Kris,Great information, thanks.My post was to clarify one main point...Is the speed displayed on the FMC approach page Vref or Vref plus the wind component that is entered on the bottom right.Based on Tim's reply earlier, it seems like Vref is being displayed with no correction.Thanks!

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Guest tmetzinger

>Just so that I fully understand.>>The Vref values displayed by the FMC do NOT have the wind>correction. However, if you leave the plane in VNAV, the wind>correction will be automatically added to Vref(flap>selection).>>If you are flying using the APPR mode, then the wind>correction factor needs to be applied to displayed Vref via>SPD?>>Thanks!>>JeffCorrectamundo! on an ILS, you dial in the speed on the MCP, and the "ref" bug on the speed tape is Vref without any correction.

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Guest FRI737

Kris,thanks for the description. The speeds you use are according to the 737-300 Flap Maneuvering Schedule, aren

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Guest Zapper

For Stefan:If you do find yourself intercepting from below then I fly up to the GS at Flap 5 and at the Flap5 speed indicated on the speed tape in PFD. Note the wind additive does not move the speed tape bug at anything other than teh Line Selected Landing Flap.We (at Pacific Blue) do not use VNAV once any flap has been selected as a result of a Boeing Service Bulletin regarding the enhanced MCP we have fitted. It has a small software glitch that will be corrected soon. And to be honest I prefer to fly an ILS using teh LOC/GS rather than LNAV/VNAV.However, if I am at say 2000'AFE or higher then I will fly down the GS at Flap 5 speed till I reach about 1200' AFE (Above Field Elevation) and then go Gear and Flap 15, checklist and then Landing Flap by 1000' etc.To fly just a few knots faster when level is of no real advantage as it saves no measurable amount of time and only increases flap track wear etc.Speed selection at commencment of approach is pilot preference although some places may have an ATC requirement for say 160kts to the Outer Markeror in that most ridiculous of places (Stdney) you are required to fly 250kts when being vectored downwind, 230 on Base and 21o uup to 10nm from teh runway. In these cases I will fly say Flap 1 or Flap5 and the slightly higher speed to meet ATC requirement.Sorry if I have caused any confusion.

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Guest Zapper

Stefan,In response to ur Q about teh lower speed schedule for teh NG.In the 300 we used a fixed speed schedule as outlined by Kris. It varies with weight ie: is 210kts clean or 220kts if you are above 56080KG (I think that is teh exact figure.. Kris?) for Flap5 it is 180/190 etc etc.It is because the NG has a different wing to the Classic and also that the PFD displays exact weight manouevring speeds and these should be flown rather than the fixed speed schedule applicable to the 300-500.Make sense?Brad Marsh

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Guest FRI737

Brad,very good, thanks!So you say a Flaps 5 Maneuvering Speed of 154 Kt is normal and it

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